Dr Simon Clulow of Newcastle University has discovered Mahony's Toadlet in a swamp close to Newcastle.Source:Supplied

A NEW species of Australian frog has been discovered with an ingenious — and scandalous — method of warding off attackers.

As a last line of defence the newly discovered Mahony’s Toadlet will flash its bright orange genitalia at any animal that wants to fancy having it for dinner.

The exposing amphibian was discovered not in a remote waterway or deep in the jungle but on the outskirts of Newcastle, the second city of NSW.

An expert in ecology at the University of Newcastle, Dr Simon Clulow, told news.com.au a group of scientists was surveying amphibians in a swamp north of the city when they came across the new species.

“We found the frog and knew straightaway it was something different”.

Most new frog species look almost identical to those already discovered and you only find the differences on a genetic level.

Dr Simon Clulow of Newcastle University discovered the new species frog near Newcastle Airport. Picture: Sheena Martin.Source:Supplied

But this wasn’t so with the testicle bearing toadlet, which is barely bigger than an adult thumb.

“This one had a very unique belly pattern,” said Mr Clulow, “almost marble like and black and white which is unusual.”

Dr Clulow said the frog’s first line of defence was that they visually mimicked their natural surroundings to avoid detection — a natural defence mechanism particularly common in small lizards, snakes and frogs.

But if that plan failed, it had another trick up its sleeve, or, if you like, down its pants.

“It’s got this bright orange rust colour in its groin. They remain hidden when it’s sitting in its normal pose so it’s very well camouflaged,” he said.

“But when it jumps you get a bright flash of colour from its groin and that startles the predator.”

“Mike has spent his life and career dedicated to study Australia’s unique wildlife and frogs and he himself has discovered numerous species.”

Both male and female toadlets have the same in your face method of exposing their genitalia. But male frogs looking for a mate need to try harder than merely putting their tackle on the table.

Rather they used distinctly unromantic vocal calls to attract the ladies.

“For such a small frog it can make an awful racket,” Mr Clulow said.

He described the mating a call as akin to a “squelching rasp”.

“When you hear you certainly know about it.”

The costal swamp lying on a sandy substrate, close to Port Stephens, was perfect conditions for the frog, said Mr Clulow. But encroaching housing development and sand mining meant the future for Mahony’s Toadlet could be bleak even though its only just been discovered.